1. Field of the Invention
The invention relates to electronic driving devices, and particularly to a device for driving a light source such as a discharge lamp of a liquid crystal display (LCD) panel.
2. Related Art
Conventionally, discharge lamps such as cold cathode fluorescent lights (CCFLs) have been used as light sources for liquid crystal display (LCD) panels. Because a plurality of discharge lamps are required for sufficient light intensity in each LCD, high voltages must be added to two ends of each discharge lamp in a large LCD panel. However, impedance differences of the discharge lamps cause unbalanced current flowing through the discharge lamps. The imbalance not only affects luminance uniformity of the LCD panels, but also shortens lifetime of discharge lamps due to large current.
To solve the above problem, a conventional device for driving discharge lamps utilizes a plurality of transformers to balance the current flowing through the discharge lamps.
FIG. 5 is a conventional device for driving discharge lamps. The device includes two direct current (DC) power sources 50 and 50′, two DC to alternating current (AC) converters 51 and 51′, a plurality of transformers T5n and T5n′ (n=1, 2, 3, . . . , n), a plurality of feedback circuits 52 and 52′, and a plurality of discharge lamps L5n(n=1, 2, 3, . . . , n). The device is divided into a left part and a right part with the discharge lamps L5n(n=1, 2, 3, . . . , n) disposed therebetween. Components of the left part and the right part are the same. The DC/AC converters 51 and 51′ respectively convert DC signals received from the DC power sources 50 and 50′ to AC signals. The transformers T5n and T5n′(n=1, 2, 3, . . . , n) convert the AC signals to sine wave signals respectively added to two ends of each discharge lamp. The feedback circuits 52 and 52′ feed back the current flowing through each discharge lamp to the DC/AC converters 51 and 51′.
In the conventional device, the current flowing through the discharge lamps is balanced by the transformers. However, cost of the device is high, and a circuit structure is more complex due to more transformers being used. In addition, a yield rate is lowered when the devices are mass-produced.